1. Field of the Invention
The present invention relates generally to a process system, equipped with a transfer unit for an object to be processed, such as a semiconductor wafer, for carrying out a predetermined process for the object.
2. Description of the Related Art
In general, in order to produce a semiconductor integrated circuit, various processes, such as deposition, etching, oxidation and diffusion, are carried out for a wafer. In addition, in order to improve throughput and yields by the scale down and high integration of the semiconductor integrated circuit, a so-called clustered-process-system has been proposed. In such a process system, a plurality of process chambers for carrying out the same process or different processes are connected to each other via a transfer chamber so that processes in various processes can be sequentially carried out without the exposure of the wafer to the atmosphere.
FIG. 8 is a schematic diagram showing an example of such a conventional clustered-process-system. As shown in this figure, a process system 2 comprises three process chambers 4A, 4B and 4C, and two cassette housing chambers 12A and 12B. The process system 2 also comprises a first transfer chamber 10, a second transfer chamber 6 and two load-lock chambers 8A and 8B having a preheating or cooling mechanism.
The three process chambers 4A through 4C are connected to the second transfer chamber 6. The two load-lock chambers 8A and 8B are provided in parallel between the first and second transfer chambers 10 and 6. The two cassette housing chambers 12A and 12B are connected to the first transfer chamber 10. Between the respective chambers, gate valves G capable of being airtightly open and closed are provided.
First and second articulated transfer arms 16 and 14 capable of bending, stretching and rotating are provided in the first and second transfer chambers 10 and 6, respectively. By holding and transporting a semiconductor wafer W by these transfer arms 16 and 14, the semiconductor wafer W is transferred. In the first transfer chamber 10, an aligning unit 22 comprising a turntable 18 and an optical sensor 20 is provided. The aligning unit 22 is designed to rotate the wafer W, which is introduced from the cassette housing chamber 12A or 12B, to detect the orientation flat or notch of the wafer W to align the wafer W.
With respect to the process of the semiconductor wafer W, an unprocessed semiconductor wafer W is first taken out from a cassette in any one of the cassette housing chambers, e.g., a cassette C in the cassette housing chamber 12A, by means of the first transfer arm 16 in the first transfer chamber 10, which is held at atmospheric pressure in an atmosphere of N2, to be mounted on the turntable 18 of the aligning mechanism 22 in the first transfer chamber 10. While the turntable 18 rotates to align the wafer W, the transfer arm 16 stands by without moving. The time required to carry out the alignment is, e.g., about 10 to 12 seconds.
After the alignment of the wafer W is completed, the standby transfer arm 16 holds the aligned wafer W again, and introduces the wafer W into any one of the load-lock chambers, e.g., the load-lock chamber 8A. In the load-lock chamber 8A, the wafer W is preheated if necessary, while the interior of the load-lock chamber 8A is evacuated to a predetermined pressure. The time required to carry out the preheating or evacuation is, e.g., about 30 to 40 seconds.
If such a preheating operation is completed, the load-lock chamber 8A is communicated with the second transfer chamber 6, which is previously held in a vacuum state, by opening the gate valve G. Then, the preheated wafer W is held by the second transfer arm 14 to be transferred into a predetermined process chamber, e.g., the process chamber 4A, in which a predetermined process, e.g., a process for depositing a metal film or insulating film, is carried out. The time required to carry out this process is, e.g., about 60 to 90 seconds.
The processed semiconductor wafer W is introduced into, e.g., the original cassette C in the cassette holding chamber 12A, along the reverse route of the above described route. In the route for returning the processed wafer W, the wafer W is transferred after being cooled to a predetermined temperature using, e.g., the other load-lock chamber 8B. The time to cool and return the wafer W to atmospheric pressure is about 30 to 40 seconds. Alternatively, before the processed wafer W is introduced into the cassette C, the wafer W may be aligned by the aligning mechanism 22 if necessary.
Furthermore, when the semiconductor wafer W is oxidized or diffused, there are some cases where it is not required to hold the transfer unit at a reduced pressure atmosphere. In that case, there are some cases where a buffer part capable of causing a plurality of wafers W to stand by for timing is provided in place of the load-lock chambers 8A and 8B capable of being evacuated.
By the way, in a process system of this type, in the above described case, the time required to treat a single wafer W is, e.g., about 60 to 90 seconds, which is some longer than the time required to carry out the alignment or preheating, although it depends on the contents of process. Therefore, the plurality of process chambers 4A through 4C are provided to effectively carry out operations. As a result, there is a problem in that the throughput of products is rate-controlled by the transfer time for the wafer W in the transfer unit. For example, during the introduction of the wafer W, until the alignment of the wafer W is completed after the wafer W is mounted on the turntable 18 of the aligning mechanism 22, the first transfer arm 16 stands by without moving and can not other transfer operations. In addition, after the alignment of the wafer W is completed, the first transfer arm 16 is monopolized to transfer the wafer W to the load-lock chamber 8A.
For such a reason, since the transfer arm is not efficiently used, there is a problem in that it is not possible to sufficiently improve throughput. In addition, since the number of delivery operations of the wafer is relatively large in the above described wafer transfer unit, aligning errors are accumulated every delivery operation, so that there is also a problem in that the final precision of the alignment deteriorates.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a so-called cluster-tool-type process system capable of efficiently transferring an object to be processed, to improve the throughput in the process for the object and to improve the precision of the alignment for the object.
In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, a process system comprises: a housing chamber for housing therein an object to be processed; a process chamber for carrying out a predetermined process for the object; a transfer chamber for establishing a communication between the housing chamber and the process chamber; a first transfer unit for delivering the object between the transfer chamber and the housing chamber; a second transfer unit for delivering the object between the transfer chamber and the process chamber; and an aligning unit for aligning the object, wherein the aligning unit is arranged in an overlapping range of transfer ranges of the first and second transfer units.
Thus, since the aligning unit is arranged in a transfer range common to the first and second transfer units, the second transfer unit can take the aligned object after the object is mounted on the aligning unit by the first transfer unit. Therefore, immediately after the first transfer unit mounts the object on the aligning unit, the first transfer unit can move to carry out the transfer operation of another object without standing by until the aligning operation is completed. As a result, it is possible to efficiently transfer the object, so that it is possible to improve the throughput in the process.
In addition, if it is not required to preheat the object in a buffer part, the aligned object can be introduced into the process chamber by a single delivery operation. Thus, it is possible to minimize aligning errors. In addition, since the object does not pass through the buffer part, it is possible to improve the transfer efficiency, so that it is possible to further improve the throughput.
The process system may further comprise a buffer part for temporarily holding the object, the buffer part being provided in the overlapping range. Thus, since the aligned object can be temporarily held by the buffer part, to which the first and second transfer units are accessible, the first and second transfer units can carry out other operations while the aligned object is temporarily held. Therefore, it is possible to enhance the utilizing efficiencies of the first and second transfer units.
The buffer part may have at least one of a preheating unit for preheating the object and a cooling unit for cooling the object. Thus, the preheating and cooling of the object can be carried out without decreasing the transfer efficiency of the object.
Preferably, the at least one of the preheating unit and the cooling unit airtightly separates the object from the transfer chamber during preheating or cooling. Thus, it is possible to prevent a gas, which has been released or exhausted from the surface of the object during preheating, and a cooling gas, which has been used for cooling, from being leaked into the transfer chamber.
The at least one of the preheating unit and the cooling unit may comprise: a closing lid capable of supporting thereon the object; a container having an opening corresponding to the closing lid; and a lift unit for vertically moving the closing lid with respect to the container, wherein when the closing lid moves upwards or downwards, the container is associated with the closing lid to airtightly separate the object from the transfer chamber.
Preferably, the process system further comprises: an additional process chamber; and an additional aligning unit, wherein each of said process chambers is provided so as to correspond to one of said aligning units. Thus, since each object-transferring route between the process chamber and the aligning unit is fixed, the aligning errors of the aligning units are not accumulated, so that it is possible to improve the final aligning precision for the object.
The predetermined process may be a process carried out under a reduced pressure atmosphere, and the interior of the transfer chamber may be maintained in a reduced pressure atmosphere.
According to another aspect of the present invention, a process system comprises: a housing chamber for housing therein an object to be processed; a process chamber for carrying out a predetermined process for the object; a transfer chamber for establishing a communication between the housing chamber and the process chamber; a first transfer unit for delivering the object between the transfer chamber and the housing chamber; a second transfer unit for delivering the object between the transfer chamber and the process chamber; an aligning unit for aligning the object; and a buffer part for temporarily holding the object, wherein the aligning unit and the buffer part are arranged in an overlapping range of transfer ranges of the first and second transfer units, the buffer part having at least one of a preheating unit for preheating the object and a cooling unit for cooling the object.
Thus, since the aligning unit is arranged in a transfer range common to the first and second transfer units, the second transfer unit can take the aligned object after the object is mounted on the aligning unit by the first transfer unit. Therefore, immediately after the first transfer unit mounts the object on the aligning unit, the first transfer unit can move to carry out the transfer operation of another object without standing by until the aligning operation is completed. As a result, it is possible to efficiently transfer the object, so that it is possible to improve the throughput in the process.
In addition, since the aligned object can be temporarily held by the buffer part, to which the first and second transfer units are accessible, the first and second transfer units can carry out other operations while the aligned object is temporarily held. Therefore, it is possible to enhance the utilizing efficiencies of the first and second transfer units. Moreover, the preheating and cooling of the object can be carried out without decreasing the transfer efficiency of the object.
Also in this case, the at least one of the preheating unit and the cooling unit may comprise: a closing lid capable of supporting thereon the object; a container having an opening corresponding to the closing lid; and a lift unit for vertically moving the closing lid with respect to the container, wherein when the closing lid moves upwards or downwards, the container is associated with the closing lid to airtightly separate the object from the transfer chamber.
In addition, the preheating unit and the cooling unit may be provided in the buffer part so as to face each other in substantially vertical directions.
According to a further aspect of the present invention, a process system comprises: a housing chamber for housing therein an object to be processed; a first transfer chamber connected to the housing chamber so as to be capable of being open and closed; a first transfer unit, provided in the first transfer chamber, for delivering the object between the first transfer chamber and the housing chamber; a process chamber for carrying out a predetermined process for the object; a second transfer chamber connected to the process chamber so as to be capable of being open and closed; a second transfer unit, provided in the second transfer chamber, for delivering the object between the second transfer chamber and the process chamber; a load-lock chamber provided between the first transfer chamber and the second transfer chamber, the load-lock chamber being capable of being evacuated; and an aligning unit, provided in the load-lock chamber, for aligning the object, wherein the aligning unit is arranged in an overlapping range of transfer ranges of the first and second transfer units.
In this case, since the aligning unit is arranged in the conventionally provided load-lock chamber, it is possible to improve the transfer efficiency of the object.